The present invention relates to an image scanner, and more particularly to an image scanner which includes a single driving device to synchronously move a transmission-mode light source and an image pickup device located on opposite sides of a scanning platform.
For an image scanner for scanning a reflective document such as a photo or a paper document, the light source 14 is generally enclosed in a carriage 15 together with an image pickup device including a mirror set 16, a lens device 17 and a charge-coupled device (CCD) 18, as shown in FIG. 1A. The light from the light source 14 is reflected off of the document 10 and received by the image pickup device 16, 17, 18 to realize the image data of the document. By moving the carriage 15 across the document 10 placed on a scanning platform 20 to be scanned, a scanning operation, so called as a reflection-mode scanning, is performed. The light source 14 is referred as a reflection-mode light source herein. Owing to the integration of the light source 14, mirror set 16, lens device 17 and CCD 18 in the carriage 15, only one driving device 12 is required to move the light source and the image pickup device across the document. The driving device 12 generally includes a motor 191 and plural gears 192.
On the other hand, for an image scanner for scanning a penetrative document such as a negative film, a projecting film or a slide, the image pickup device including the mirror set 16, lens device 17, and CCD 18 is enclosed in the carriage 15, and the light source 13 is disposed opposite to the carriage 15 relative to the scanning platform 20, as shown in FIG. 1B. The light from the light source 13 penetrates through the document 10 and received by the image pickup device 16, 17, 18 to realize the image data of the document. By moving the carriage 15 across the document 10 placed on the scanning platform 20 to be scanned, a scanning operation, so called as a transmission-mode scanning, is performed. The light source 13 is referred as a transmission-mode light source herein. Owing to the separation of the light source and the image pickup device, one driving device 11 is required to move the transmission-mode light source 13, and another driving device 12 is required to move the carriage 15.
For a dual-mode image scanner, a transmission-mode scanning or a reflection-mode scanning is performed optionally. For sharing a single image pickup device which is relatively expensive, both of the transmission-mode and the reflection-mode light sources are required, as shown in FIG. 1C. In the conventional dual-mode image scanner, the two driving devices 11 and 12 are used to move the transmission-mode light source 13 and the reflection-mode light source 14 which is mounted in the carriage 15 together with the mirror set 16, the lens device 17 and the CCD 18, respectively. According to the type of the document 10 to be scanned, either one of the transmission-mode light source 13 and the reflection-mode light source 14 is energized. When a transmission-mode scanning is performed, it is necessary for the transmission-mode light source 13 to be synchronously moved with the carriage 15 in order to allow the light emitted therefrom and penetrating through the document 10 to precisely reach the mirror set 16 and further the lens device 17 and the CCD 18. In other words, it is important to perfectly synchronize the movement of the light source 13 with that of the carriage 15. However, such a synchronizing operation is not easy to achieve. Further, owing to the presence of two driving devices including motors 191 and gears 192, the image scanner may be undesirably bulky.
For reducing to a single driving device, a driving mechanism as shown in FIG. 2 is suggested to simultaneously move the transmission-mode light source and the carriage. Similar to the image scanner of FIG. 1, the reflection-mode light source (not shown) is mounted in a carriage 25 which is moved by a driving device. In this image scanner, two guiding slots 211 beside the scanning window 29 are created, and two connecting rods 212 are provided. The two opposite connecting rods 212 penetrate the slots 211 and connect the transmission-mode light source 23 to the carriage 25. With the driving of a motor and gears (not shown, with reference to FIG. 1), the carriage 25 transmits the light source 23 connected therewith through the connecting rods to move synchronously. Therefore, only one set of driving motor and gears is required, and no misalignment problem will occur. U.S. Pat. No. 5,251,072, which is incorporated herein for reference, also describes a similar driving mechanism to synchronize the movement of the transmission-mode and the reflection-mode light sources.
The image scanner of FIG. 2, though omitting one set of motor and gears to possibly reduce the thickness of the scanner housing, requires additional width to create the two guiding slots. Furthermore, the presence of the guiding slots renders contaminants such as dusts to have a chance to enter the lower housing where the important optical devices are accommodated.
Therefore, an object of the present invention is to provide a dual-mode image scanner, in which a single driving device is used to synchronize the movement of a transmission-mode and a reflection-mode light sources without creating any long slots beside a scanning window.
Another object of the present invention is to provide a transmission-mode image scanner, in which a single driving device is used to synchronize the movement of a light source and an image pickup device enclosed in a carriage precisely and conveniently.
According to the present invention, an image scanner includes a scanning platform for placing thereon a document to be scanned, a housing including a lower housing, and an upper cover pivotally connected to the lower housing at an upper end of the scanning platform, a transmission-mode light provider accommodated in the housing for providing a light signal for the document to be scanned, an image pickup device accommodated in said housing at a side of the scanning platform opposite to the transmission-mode light provider for receiving an image signal from the document in response to the light signal, and converting the image signal into an electronic signal, and a driving device connected between the transmission-mode light provider and the image pickup device for synchronously moving the transmission-mode and the image pickup device.
According to the present invention, the driving device includes a driving element for simultaneously providing a driving force for the transmission-mode light provider and the image pickup device, a first transmission device connected between the driving element and the image pickup device for moving the reflection-mode light provider in response to the driving force, and a second transmission device connected between the driving element and the transmission-mode light provider for moving the transmission-mode light provider in response to the driving force.
According to the present invention, the first or the second transmission devices penetrates through the scanning platform at the upper end, depending on the positions of the transmission-mode light provider, the image pickup device, and the driving element.
For example, if the transmission-mode light provider is located in the upper cover, and the driving element and the image pickup device are located in the lower housing, then the first transmission device are located in the lower housing, and the second transmission device penetrates through the scanning platform at the upper end.
Preferably, the driving element is a motor.
Preferably, the second transmission device includes a roller mounted in the lower housing beneath the upper end of the scanning platform, and driven to rotate by the motor, a first pulley mounted in the upper cover above a lower end of the scanning platform opposite to the upper end, and a cyclic transmission line penetrating through the scanning platform, attached thereto the transmission-mode light provider, hitching the first pulley and the roller, and rotating with the roller with the aid of the first pulley for moving the transmission-mode light provider across the scanning platform.
Preferably, the cyclic transmission line is made of a flexible material. More preferably, the second transmission device further includes two second pulleys arranged between the roller and the first pulley and adjacent to the upper end of the scanning platform for sustaining thereagainst the cyclic transmission line when the upper cover is lifted. Particularly preferably, the cyclic transmission line is inserted thereinto a section of buffering device, e.g. a stretching spring element, for improving the tensile strength thereof so as to minimize vibration of the transmission-mode light provider resulting from the driving force.
Preferably, the image pickup device is mounted in a carriage which is connected to and moved by the first transmission device.
If the image scanner further includes a reflection-mode light provider to function as a dual-mode image scanner, the reflection-mode light provider is preferably mounted in the carriage.
The types of the transmission-mode light provider and the reflection-mode light provider may vary.
In an embodiment, the transmission-mode light provider includes a first lamp energized to provide the light signal for the document when a transmission-mode scanning operation is performed, and the reflection-mode light provider includes a second lamp energized to provide the light signal for the document when a reflection-mode scanning operation is performed. U.S. Pat. No. 5,251,072 provides an example for these types of transmission-mode and the reflection-mode light providers.
In another embodiment, the transmission-mode light provider includes a first lamp energized to provide the light signal for the document when a transmission-mode scanning operation is performed, and the reflection-mode light provider includes a mirror set reflecting light from the first lamp to the document as the light signal when a reflection-mode scanning operation is performed. A pending U.S. patent application Ser. No. 09/007,641, which is assigned to the same assignee as the present application and is incorporated herein for reference, provides an example for these types of transmission-mode and the reflection-mode light providers.
In a further embodiment, the reflection-mode light provider includes a second lamp energized to provide the light signal for the document when a reflection-mode scanning operation is performed, and the transmission-mode light provider includes a mirror set reflecting light from the second lamp to the document as the light signal when a transmission-mode scanning operation is performed. U.S. Pat. No. 5,895,914, which is incorporated herein for reference, provides an example for these types of transmission-mode and the reflection-mode light providers.